Tunnel extremely soft rock stratum shrinkage arch frame primary supporting method

Abstract

The invention discloses a tunnel extremely soft rock stratum shrinkage arch frame primary supporting method. According to field verification, extremely soft carbon shale and argillaceous shale have the characteristics of plastic rheology, water adsorption and water permeation, on the basis of the characteristics, a primary supporting structure measure is taken from the viewpoint of taking resistance as the main and proper release as the auxiliary, large deformation, primary support limit invasion and collapse of soft rocks can be treated according to indications, the measure is reliable and effective. The tunnel extremely soft rock stratum shrinkage arch frame primary supporting method has the advantages that the reserved settlement deformation amount is properly increased on the basis oforiginal design primary support, so that limit invasion and rework are eradicated on the basis that certain deformation is allowed, the construction speed is increased, and the serious tension degreeof the construction period on a whole railway line is relieved; and in addition, a size-limited shrinkage arch frame is simple in design and machining and convenient to operate in site construction.

Description

technical field [0001] The invention relates to the technical field of tunnel construction, in particular to a method for initial support of a contracted arch frame in extremely soft rock strata of a tunnel. Background technique [0002] A high-speed railway double-track tunnel is located in the Jingshan Mountains, which is a structurally denuded low-mountain landform area. The tunnel body passes through the sandy shale of the Xintan Formation (S1x), such as figure 1 shown. The tunnel site area is located at the northern edge of the first-order tectonic unit of the Yangtze quasi-platform, within the Shennongjia-Jingmen platform fold belt of the Upper Yangtze continental block fold belt. The main types of groundwater are Quaternary pore phreatic water and bedrock fissure water. Atmospheric precipitation and surface water are the main sources of groundwater supply in the area. [0003] The tunnel is divided into three work areas, entrance, cross tunnel and exit, and the con...

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Problems solved by technology

However, this existing scheme has the following disadvantages: ①The amount of reserved settlement deformation is too small. After the first initial support, about 95% of the initial support deformation cracks, invades, and reworks, resulting in multiple landslides, and the safety risk is too high. At the same time, it will seriously affect the construction progress and increase the construction cost.

② There is no strengthening of the primary support. It is only a subjective perception that as long as the pressure of the rock formation is released and the deformation of the primary support is allowed, it will tend to be stable. However, the high safety risk has not been eliminated.

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